Simplify the following expression: $r = \dfrac{-2x - 9}{7x + 8} - \dfrac{-1}{7x + 8}$
Explanation: Since the expressions have the same denominator we simply subtract the numerators: $r = \dfrac{-2x - 9 - (-1)}{7x + 8}$ Distribute the negative sign: $r = \dfrac{-2x - 9 + 1}{7x + 8}$ Combine like terms: $r = \dfrac{-2x - 8}{7x + 8}$